Bonneville America Forums Forums Technical Forums General Tech Stock pilot size?

Google seems no help here. Some place's say 40 some 42. What is stock? I thought they were 42 and have ordered some 45's from Eddy but now am wondering if they will be too big?. Currently running 3 1/4 turns out and almost have popping stopped. Was 2 1/2 but was just awful noise on the over run. See my signature for other settings

OEM spec 790 was 42; OEM spec 865 was 40

Cheers for that. So I'm running 40's. might get a set of 42's sent over, just as well they are cheap and it keeps Eddy in beers.....

Assume nothing unless personally verified.

Oh for sure. but its fiddly enough so will get the 42's before getting in there.

Depending on your elevation and mods 42 will probably be a bit small too. You will need to adjust the mixture screws too.

Keep in mind OP is running DJ needles.

Just a quick recap of my set up. TOR's with holes drilled in rear baffle (packing has finally all blown out). K&N Filter with snorkel removed and opening filed down to allow largest possible opening. AI removed. DJ Stage one kit( DJ needles and springs,clip one from bottom, 126 main DJ jet). Had mixture screws at 2 1/2 out but as pipe baffles have blown out over run backfiring has become horrible. Screws currently at 3 1/4 turns out. Just about eliminated the backfiring. Had thought I had 42 pilots as stock, hence ordering 45's, but may have only 40's as that's stock. Bike has always run very well and amazingly strongly with good milage, just trying to eliminate the backfiring. Does seem a bit stronger down low since I have opened up the mixture screws though. So if I do indeed have 40's (unless changed when the TOR's went on by previous owner) then 42's may be all I need. I know when I opened up the intake side it was running stock mains, I never actually looked at the pilots. Used Dinquas calculator, (that's where I got the 42's as stock idea). So there you go......

OK, may have to mess with your needles as well as your main jet too to get it right. I still say chances are the right pilot will be 45, doubt 48 like I run since there is more restriction than I have. Kills me how many people always say that the bike runs great. A lean bike will run better than a properly jetted one sometimes until the damage is done. Then it's too late. Our engines seem to be somewhat forgiving in that department though as I know some on here are very lean from what they have posted as their set up and the engines seem to be holding up. Seems more often than not people guess on the idle mixture too instead of a proper adjustment going by backfire on decel. If it is completely eliminated the jetting is wrong with a low restriction exhaust. Should be no real backfires but a kind of rumble so to speak, hard to explain the sound. Excessive backfiring could be an indication of a lean condition or an exhaust leak for most common causes. The properly adjusted idle mixture should be around 2 to 3 turns out much more than 3 and you should go up one pilot size. Since the pilot effects more than just idle you will need to compensate with the rest of your set up too if you want to get it right.

Awesome. Thanks for the input Dog. Will put the 45's in once they arrive and go from there.

Always start with the pilot since that effects your idle when all is closed. If you start with needles and mains then the pilot you will have to go back and adjust the rest as the change in pilot will change the adjustment on the rest. Keep in mind, as I stated earlier in the thread, your elevation changes the size jets you need. If you are at a high elevation you will need smaller jets than if you are at sea level.

With DJ needles, if the existing pilots are 40's then I would first suggest trying 42's...however, if the current pilots are 42's, then go to 45's.

While I agree that the 42 may be right for him, the DJ needles have no bearing on what the correct pilot would be.The reverse is true however since it will effect the AF up to about 1/2 throttle. You have to get the pilot right first then you have to adjust the mains and needles with the correct pilot in place. That is the only way to get a proper adjustment. If you start with the pilot wrong and get the rest right then go back and fix the pilot the rest will be off again. Personally I start with a completely stock set up then get the pilot right then on to the main jet, then on to the needle and maybe spring combination, then back to the main if need be etc.. until I have what I want. Lets not forget the air hole in the slide too, not sure when the updated larger size was stock.

We can disagree on that, as I have no need to argue that opinion.

Thanks for all the input guys. From the way I set up according to the calculator my mains should be pretty close ( I know its not exact, but a starting point). Its just that i worked off having 42 pilots, if I do have the 40's then that explains my leanness down low. Once both sets of jets arrive I will be into it and will fit which ever is the next size up and go from there.

Well due to what ever controls international mail my 42's which were ordered a week after the 45's turned up today (still waiting on the 45's). I did indeed have the stock 40's. Have now fitted the 42's and initially set the screw at 2 1/2 turns. Definate improvement in the backfiring. Went to 2 3/4 turns and only had a back fire twice on my test circuit. Balanced the carbs when I got back and they were out quite a bit. Haven't had a chance for another ride yet, but looking good. Need to go for just a ride, these 'test' rides are all well and good but I find myself trying to induce the backfiring, just need to forget that and see how it goes. Pretty happy so far though.

I think much over 3 turns and you should go up one size but could get away with 4 probably if you had to. Why not actually do a proper adjustment on the pilot screws rather than guessing. Backfire is not a good adjustment method.

Not sure if you already tried this but disconnect the Throttle Position Sensor (unplug the little triangle plug). That will get rid of the backfiring. Many have done it. Check the search engine.